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Shell command: timedatectl

timedatectl controls (querying and changing) the system date and time.
Executing timedatectl might print something like. 
                      Local time: Wed 2018-10-10 03:48:10 UTC
                  Universal time: Wed 2018-10-10 03:48:10 UTC
                        RTC time: Wed 2018-10-10 03:48:11
                       Time zone: UTC (UTC, +0000)
       System clock synchronized: no
systemd-timesyncd.service active: no
                 RTC in local TZ: no
Note, that it reports that the system clock is not synchronized.
Ensure that the system clock is accurate: 
timedatectl set-ntp true
Now, it prints 
                      Local time: Wed 2018-10-10 03:55:44 UTC
                  Universal time: Wed 2018-10-10 03:55:44 UTC
                        RTC time: Wed 2018-10-10 03:55:44
                       Time zone: UTC (UTC, +0000)
       System clock synchronized: yes
systemd-timesyncd.service active: yes
                 RTC in local TZ: no

See also

hwclock
Shell commands

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